Colonic transport of water and electrolytes in a patient with secretory diarrhea due to collagenous colitis

Abstract

Whole colon perfusion studies and measurements of luminal prostaglandin E2 were carried out in a 41-year-old female with collagenous colitis to investigate pathophysiological mechanisms for the diarrhea. Biopsies of the colorectal mucosa had revealed a continuous 25- to 60-micron subepithelial collagenous layer, but normal junctional complexes and capillaries. When the patient fasted, the diarrhea persisted and fecal electrolytes, as estimated from the concentration of sodium, potassium, and their anions, accounted for all the osmolality (284 mosm/kg) of stool water, the pH of which was above 8.0. The lumen-negative electrical potential difference in the rectum was -64 mV vs -45 +/- 2 mV (mean +/- SEM) in healthy controls. Profuse secretion of fluid and electrolytes occurred during colonic perfusion with saline. Transport of sodium appeared to be passive with flux ratios equal to those predicted for passive sodium movements, while chloride transport against a steep electrical gradient indicated active secretion. Perfusion with an "ileal output"-like solution decreased fluid and electrolyte secretion, suggesting that bicarbonate, in addition to chloride, may be a major determinant of secretion rates. Since immunoreactive prostaglandin E2 levels following in vivo equilibrium dialysis of feces ranged from 555 to 650 pg/ml vs 55 to 235 pg/ml (99% confidence limits) in healthy controls, it is speculated that prostaglandins synthesized locally in response to mucosal hypoxia might be the mediators of anion secretion.

Collagenous colitis associated with small intestinal villous atrophy.

“…8 Collagenous colitis is diagnosed by histological examination of colonic biopsies, which shows the characteristic band of collagen deposited beneath the epithelial basement membrane, usually associated with a non-specific chronic inflammatory infiltrate. The relationship between the inflammatory reaction, the collagen deposition and the development of symptoms is uncertain, and the stimulus to collagen deposition is also unknown.…”

Effect of Fasting on Diarrhoea in Collagenous Colitis

“…Perfusion studies in 4 patients showed net secretion of fluid and electrolytes in the colon and the small intestine and no sodium absorption in the colon [5, 6, 7]. In one of these patients, diarrhoea persisted during fasting [7]. In another study fasting normalised stool output in 2 of 4 patients [8].…”

“…There are only a few reports concerning the mechanisms of diarrhoea in CC. Perfusion studies in 4 patients showed net secretion of fluid and electrolytes in the colon and the small intestine and no sodium absorption in the colon [5, 6, 7]. In one of these patients, diarrhoea persisted during fasting [7].…”

“…A study on faecal stream diversion strongly indicated that an unknown luminal agent can exert a specific mucosal reaction leading to CC in predisposed subjects [4]. Pathophysiological studies including intestinal perfusion have only been carried out in 4 CC patients, indicating that the diarrhoea might be of a secretory nature [5, 6, 7]. Many patients with CC, however, report that fasting reduces the diarrhoea and, in one study, fasting normalised stool output in 2 of 4 patients [8].…”

Are Collagenous Colitis and Lymphocytic Colitis Distinct Syndromes?

“…Colonic perfu sion studies have demonstrated profuse secre tion of fluid and electrolytes in collagenous colitis. Transport of sodium appears to be pas sive, while chloride transport is active and occurs against a steep electrical gradient [29], The local prostaglandin E2 level is increased in some patients and may be the mediator in the secretory diarrhea. Ei levels have been ele vated in jejunal aspirates and stools in some patients [26].…”